A hernia is a failure of a body barrier to restrain the protrusion of organs from one area into another. Normally, the anterior (front) abdominal wall restrains abdominal contents, including intestine, from protruding through the muscles and fascia to a position under the skin. In ventral hernias, the abdominal wall has separated and intestine or other contents herniate through the weakness to a subcutaneous position on the abdominal wall. The muscular separation is called the hernia defect. As the intestines protrude through the hernia defect, they come to rest in the fatty soft tissue under the skin called subcutaneous fascia. The volume of intestine that protrudes through the muscular or fascial defect is called the hernia volume, or sometimes the hernia sac.
Ventral hernias refer to any hernia through the anterior abdominal wall. They can arise spontaneously. More commonly, ventral hernias arise in an area of a previous surgical incision through the muscles and fascia of the abdominal wall and are called incisional hernias. They arise because even though the skin of an incision has healed, the area where the deeper muscles and fascia were originally sewn together separates over time, allowing the intestines to protrude.
Ventral hernias cause problems because they are painful, unsightly, and represent a threat to the patient. If the herniating intestines get strangled by the constricting hernia defect border, intestinal death can occur. Incisional hernias arise as a long-term complication after abdominal surgeries, in about 10-20% of abdominal surgery patients. It is estimated that one hundred thousand hernia meshes are placed annually in the United States for ventral hernia repairs.
All ventral hernias, except for small spontaneous (umbilical or epigastric) hernias, require mesh for repair. Umbilical and epigastric hernias also require mesh repair when they are larger than 2 cm diameter. The mesh is made of some type of strong synthetic, or biologic, fabric-like material.
Ventral hernias can be repaired by open or laparoscopic techniques. In open technique, an incision is re-made directly through the original incision that caused the hernia. The hernia sac is dissected from the surrounding subcutaneous fascia and the fascial edges of the hernia defect are defined. The surgeon places a mesh into the abdomen, through the opened hernia defect. A flat mesh is chosen so that its area overlaps the edges of the defect from behind, for a few centimeters in all directions from the defect edges. It is sewn in place behind the defect and usually inside the abdomen.
In a laparoscopic repair, an incision going through the prior skin incision site is avoided. Fiberoptic cameras and small plastic ports are used to perform surgery inside the abdomen. The ports are placed through small incisions, away from the original surgery site. The abdomen is inflated like a tent and a camera is used to see inside the abdomen. In laparoscopy, the view towards the “ceiling” shows the posterior aspect of the anterior abdominal wall. Any bowel herniating into the defect at the time of surgery is removed, exposing the hernia defect and sac. The defect size is approximated and a suitable-size mesh is chosen to be placed in the abdomen. Like in open hernia repairs, the mesh must overlap the defect edges by a few centimeters in all directions. It is sewn or tacked in place against the posterior aspect of the anterior abdominal wall.
After open or laparoscopic ventral hernia surgery, the hernias still recur in 10-30% of cases. Such surgeries fail because the mesh fails to keep the bowel out of the hernia defect. Sometimes the mesh does not overlap the defect widely enough when sewn in place. Sometimes gaps form between the stitches or tacks holding the mesh in place and the bowel works itself between the gaps. Sometimes the mesh twists, kinks, or retracts in some way, permitting bowel access to the defect. The high failure rate is considered a major surgical problem in hernia surgery.
Irregular or multiple defect areas and irregular hernia sac volumes contribute to recurrence after repair. A large incisional hernia often consists of a dominant, more obvious defect, accompanied by smaller defects, not initially appreciated before surgery. These smaller defects are well known to surgeons and the problem is often referred to as a “Swiss Cheese” defect because of the multiple holes. The multiple volumes and areas often require open-style surgery to use larger incisions and meshes than initially expected, with increased associated morbidity from the large incision. The multiple volumes and defects also make placement of the hernia mesh difficult to gauge laparoscopically, where appropriately-sized meshes and their placements are selected on the basis of indirect visualization techniques.
In both open and laparoscopic procedures, significant time is spent measuring and estimating defect size, and then fixing the mesh in place using through-and-through sutures to the normal abdominal wall muscles at the edge of the hernia defects. Since the hernia defect area is covered from behind by conventional laparoscopic ventral hernia meshes, but the hernia sac volume isn't “filled,” the sac volume always fills with blood or serum (forming a hematoma, or seroma, respectively). In open repair, the problem can be avoided by placing suction drains between the skin and the mesh to drain and collapse hernia sac space. The drains are unsightly, uncomfortable, and importantly may contribute to mesh infection, a difficult complication. Drains are not placed in a laparoscopic repair, but seromas and hematomas are unavoidable. Therefore, there exists a need for a new hernia mesh that can exactly and easily fit into hernia sac and collapse the hernia sac space permanently.